Puncher

ABSTRACT

A puncher is used when piercing a workpiece with a piercing punch while the workpiece is kept pressed by a stripper. The cover provided on the puncher is made of metal and a diameter of a cover portion at and near a tip end side is smaller than that of the other cover portion other than the cover portion. The other cover portion of the cover receives a biasing member. The cover portion at a tip end side gradually reduces its diameter toward the tip end to form a tapered portion. The puncher provides a long lifetime, guarantees sufficient pressing force onto a workpiece, and punches a hole at a position near and nearer a corner of the workpiece having adjacent metal plate surfaces forming an angle of from 90 degrees to 95 degrees at the corner.

FIELD OF THE INVENTION

The present invention relates to a puncher for piercing a workpiece with a piercing punch while a stripper is pressing the workpiece.

BACKGROUND OF THE INVENTION

A conventional piercing puncher 9 is disclosed, for example, in Japanese Patent Application Laid Open No. 2006-61938 (refer to FIG. 3).

The puncher 9, shown in FIG. 7, includes a cylindrical cover 90 with a one-end opening hole 90 a, a piercing punch 91 a tip end of which is protruded from the one-end opening hole 90 a and which is loosely but not removably inserted with respect to the cover 90 by means of a punch retainer 94, and a cylindrical stripper 92 provided between the cover 90 and the piercing punch 91 in a retaining state, and the stripper 92 is protruded more than the piercing punch 91 from the one-end opening hole 90 a by a compression coil spring 93 (a biasing member). When the stripper 92 is pressed in and down against biasing force of the compression coil spring 93, an end surface 91 a of the piercing punch 91 is protruded out from a through-hole 92 a formed at a protruding end of the stripper 92. In FIG. 7, there are shown a supporting plate 95 attached to the cover 90 with a bolt B1, a positioning pin PN for positioning the puncher 9 relative to an upper die, and a bolt B2 for attaching the puncher to the upper die.

With this puncher, while the stripper 92 presses the workpiece, the piercing punch 91 pierces the workpiece.

Therefore, this puncher 9 provides advantages shown below.

(1) When piercing, the workpiece is pressed only at a minimal portion necessary for piercing, so that the portion to be machined could be made as small as possible and piercing may be done at a lower cost.

(2) Since the puncher could be downsized, a plurality of adjacent holes may be punched with one puncher.

However, the foregoing puncher 9 has a problem that it is difficult to punch a hole at a position near a corner of the workpiece where adjacent metal plate surfaces form the corner with an angle of from 90 degrees to 95 degrees (in many cases, from 90 degrees to 93 degrees, which holds true hereinafter). This is because a peripheral surface of the cover 90 bumps the metal surface other than the metal surface in which a hole is to be punched.

It would be considered to make a diameter of the cover 90 smaller in order to solve the above-described problem. However, this will reduce elastic resilient force of the compression coil spring 93 within the cover 90 and resulting in another problem that a pressing force onto a predetermined workpiece cannot be guaranteed.

Further, it would be considered to make the cover 90 with a rubber material and piercing process is conducted while an outer peripheral surface of the cover is pressed against the metal plate surface by utilizing elastic deformability of the rubber. However, this will extremely shorten a lifetime of the cover 90.

Recently, in the industry using a piercing puncher is a demand for development of a puncher which (a) has a long lifetime, (b) guarantees sufficient pressing force onto a workpiece, and (c) punches a hole at a position near and nearer a corner of a workpiece having adjacent metal plate surfaces forming an angle of from 90 degrees to 95 degrees at the corner.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention is to provide a puncher which has a long lifetime, can guarantee sufficient pressing force onto a workpiece, and punch a hole at a position near and nearer a corner of a workpiece where adjacent metal plate surfaces form a corner with an angle of from 90 degrees to 95 degrees.

A puncher according to the present invention includes a cylindrical cover with a one-end opening hole; a piercing punch, a tip end of which is protruded from the one-end opening hole and which is loosely but not removably inserted with respect to the cover; a cylindrical stripper provided between the cover and the piercing punch in a retaining state; and a biasing member by which the stripper is protruded more than the piercing punch is from the one-end opening hole. When the stripper is pressed in against biasing force of the biasing member, the tip end surface of the piercing punch becomes protruded out from a through-hole formed at a protruding end of the stripper. The cover is made of metal, and a diameter of a second cover portion at and near the tip end side is smaller than that of a first cover portion other than the second cover portion.

In the puncher according to the present invention, the biasing member is received in the first cover portion. Thus, the second cover portion at the one-end opening hole side is made smaller than the first cover portion receiving the biasing member.

The second cover portion at the one-end opening hole side gradually reduces its diameter toward the opening hole side to form a tapered portion. And it is preferable to make an inclined line of the tapered portion concave inwardly.

The biasing member of the puncher of the present invention may be a compression coil spring.

Piercing process with the puncher according the present invention is conducted with a piercing punch while a workpiece is kept pressed by the stripper.

The puncher according to the present invention can provide a long lifetime, guarantee sufficient pressing force onto a workpiece, and punch a hole at a position near and nearer a corner of a workpiece having adjacent metal plate surfaces forming an angle of from 90 degrees to 95 degrees at the corner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a puncher according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the puncher.

FIG. 3 is an external perspective view of the puncher in a state in which a stripper is pressed in from the state shown in FIG. 1.

FIG. 4 is a cross-sectional view of the puncher in a state in which the stripper is pressed in from the state shown in FIG. 2.

FIG. 5 is a front cross-sectional view of a pierce die using the puncher according to this embodiment, in a top dead center state.

FIG. 6 is a front cross-sectional view of the pierce die of FIG. 5 in a bottom dead center state.

FIG. 7 is a cross-sectional view of a conventional puncher.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment will be described in detail for carrying out a puncher according to the present invention.

A puncher P, shown in FIGS. 1 and 2, includes a cylindrical cover 1 with a one-end opening hole 10; a piercing punch 2, a tip end 20 of which is protruded from the one-end opening hole 10 and which is loosely but not removably inserted with respect to the cover 1 by means of a punch retainer 5; and a cylindrical stripper 3 provided between the cover 1 and the piercing punch 2 in a retaining state, and the stripper 3 protrudes more than the piercing punch 2 does from the one-end opening hole 10 by a biasing member 4. When the stripper 3 is pressed in or down against biasing force of the biasing member 4, as shown in FIGS. 3 and 4, the tip end surface 20 is protruded out from a through-hole 30 formed at a protruding end of the stripper 3.

Especially, in the puncher P, the cover 1 is made of metal, and a diameter of a second cover portion 1 b (a portion of the cover 1) on a tip end side (where the one-end opening hole 10 is provided) is made smaller than that of a first cover portion 1 a (another portion of the cover 1) receiving the biasing member 4, as shown in FIGS. 1 to 4.

Hereinafter, main components of the puncher such as the cover 1, the piercing punch 2, and the stripper 3 will be described in detail.

The cover 1 is made of, for embodiment, carbon steel for machine structural use (S45C), and has a cylindrical portion 11 and an attaching portion 12 formed in one body with the cylindrical portion 11 at the bottom portion, as shown in FIGS. 1 and 2.

The cylindrical portion 11 includes a tip end cylindrical portion 11 a mainly receiving the stripper 3, a center cylindrical portion 11 b mainly receiving a compression coil spring 40 serving as the biasing member 4, and a base cylindrical portion 11 c mainly receiving the punch retainer 5, as shown in FIG. 2. A stepped portion 19 is formed on an inner surface portion between the tip end cylindrical portion 11 a and the center cylindrical portion 11 b of the cylindrical portion 11.

The attaching portion 12 includes, as shown in FIGS. 1 and 2, two bolt insertion holes 13, two positioning pin insertion holes 14, and one screw hole 15. When a bolt 16 is screwed into the screw hole 15, the punch retainer 5 is not removed from the base cylindrical portion 11 c by locking (locking portion k) between the bolt 16 and the punch retainer 5.

In this embodiment, as describe above, the diameter of the second cover portion 1 b on the tip end side (where the one-end opening hole 10 is provided) of the cover 1 is made smaller than that of the first cover portion 1 a receiving the compression coil spring 40, and the second cover portion 1 b gradually reduces its diameter toward the tip end side to form a tapered portion, as shown in FIGS. 1 to 4. It is preferable that an inclined line of the tapered portion is concave inwardly. The tapered portion is not necessarily required, but it is sufficient to simply make the diameter smaller. In addition, a base point from which the cover 1 reduces its diameter may be somewhat away from a position where the compression coil spring 40 is received.

The piercing punch 2 is obtained by quenching and polishing tool steel and, as shown in FIGS. 1 and 2, is retained by the punch retainer 5 with its tip end surface 20 being located within a through-hole 30 of the stripper 3 by the biasing force of the compressing coil string 40.

The stripper 3, as shown in FIG. 2, has a cylindrical shape having an peripherally protruding collar portion 31 at a rear (i.e. an inner) end side, and stands in a retaining state relative to the cover 1 by an engagement between the peripherally protruding collar portion 31 and the stepped portion 19 by biasing of the compression coil spring 40. The stripper 3 is made of high strength brass casting (CAC304), for example.

The biasing member 4 is formed with the compression coil spring 40 as described above and shown in FIG. 2, which is a general purpose article and generally and widely available. The biasing member is not limitative to a compression coil spring, but any biasing member may be used as long as it can bias the stripper 3 with a predetermined force.

The punch retainer 5 is made of carbon steel for machine structural use (S55C) and securely fixes the piercing punch 2 within the cover 1.

In this embodiment, in order to prevent the stripper 3 from rotating, as shown in FIG. 2, a groove 60 extending in an axial direction is formed on an outer peripheral wall of the stripper 3, and a screw-shaped protrusion 61 provided on an outer wall of the cover 1 protrudes into the groove 60. Such structure is not essential and may be omitted.

Usage of the puncher P is described below. FIG. 5 is a front cross-sectional view of a pierce die using the puncher according to this embodiment in a top dead center state, and FIG. 6 is another front cross-sectional view of the pierce die of FIG. 5 in a bottom dead center.

(1) First, a workpiece W is placed on a workpiece supporting member 70 fixed on a lower die substrate 7, and the puncher P is set on an upper die substrate 8 for piercing the workpiece W. The puncher P is attached to the upper die substrate 8, as shown in FIG. 5, by screwing bolts B inserted in the bolt insertion holes 13, 13 of a flange portion (the attaching portion) 12 into the upper die substrate 8, and further by driving pins PN press-fitted in the positioning pin insertion holes 14 into the upper die substrate 8.

(2) In a state where the workpiece W is placed on the workpiece supporting member 70, an upper die 80 lowers down. Then, the stripper 3 comes into contact with the workpiece W, and thereafter, the stripper 3 is pressed in and back against the biasing force of the compression coil spring 40. Here, an outer peripheral area of the portion to be pierced of the workpiece W is strongly pressed.

(3) When the upper die 80 further lowers down from the above-described state, the piercing punch 2 protrudes out from the stripper 3 and punches a hole in the workpiece W, and the upper die 80 still further lowers down to be in the bottom dead point state shown in FIG. 6.

(4) When punching is completed and the upper die 80 moves back upward, the workpiece W that has been punched and is sticking to the puncher P is separated away from the puncher P due to the stripper 3 biased downward with the compression coil spring 40.

This puncher P has the following advantageous functions and effects.

(a) Long Lifetime

An easy solution to the problem in the prior art is, as already described above, to make the cover with a rubber material and do piercing process while pressing an outer peripheral surface of the cover against a metal plate surface making use of elastic deformability of the rubber. However, this solution will raise a problem that the lifetime of the cover 9 is very short.

On the other hand, the puncher P according to the embodiment of the present invention has a very long lifetime since the cover could be made of metal material having high rigidity.

(b) Guarantee of a Sufficient Pressing Force to the Workpiece

An easy solution to the problem in the prior art is to reduce the diameter of the cover. This solution, however, also reduces elastic regression force of the compression coil spring arranged within the cover and will raise another problem that the predetermined pressing force to the workpiece is not guaranteed.

On the other hand, the puncher P according to the embodiment of the present invention, in which the diameter of the compression coil spring does not have to be smaller, may guarantee the predetermined pressing force to the workpiece.

(c) Easy Punching Near an Angled Corner

In the embodiment of the present invention, the cover 1 is made of metal, and the diameter of the second cover portion 1 b at the tip side (where the one-end opening hole 10 is provided) is made smaller than that of the first cover portion 1 a receiving the compression coil spring 40. The second cover portion 1 b reduces its diameter with a tapered portion in which the diameter gradually becomes smaller toward the tip end side, as shown in FIGS. 1 to 4. This cover portion reduced in diameter facilitates an easy punching near a angled corner.

As constructed as above, the puncher or the cover according to the embodiment of the present invention can have an extended lifetime, the puncher can guarantee the sufficient pressing force onto a workpiece, and punch a hole at a position near and nearer an angled corner of a workpiece wherein adjacent metal plate surfaces form a corner with an angle of from 90 degrees to 95 degrees.

In addition, a portion corresponding to the tapered portion may simply reduce in diameter, which also functions likewise.

In the puncher P according to the present invention, a design thereof may be freely modified, for example, as described below, except that the cover 1 is made of metal, and that the diameter of the cover portion at and near the one-end opening hole is made smaller than that of the other cover portion other than the cover portion.

Although the cover 1 and the attaching portion 12 are made in one body in the above embodiment, they may be formed separately and put together with a bolt.

There are two bolt insertion holes 13 in the above embodiment, but the number of the holes is not limitative thereto and may be one or three.

Specifically, the puncher P according to the present invention is used when punching a hole for fitting rubber materials to be stretched on an inside of an automobile door so as to prevent rain or wind from entering inside of the automobile from outside. A metal plate to be punched generally has a small width, and existence of another metal plate adjacent to it, the two of which form a corner with an angle of from 90 degrees to 93 degrees, makes punching very difficult.

However, in the puncher P according to the present invention, the first cover portion 1 b with the reduced diameter facilitates to punch a hole at a position closer to a corner of the metal plate surfaces in a workpiece (see FIG. 6). As a result, holes for fitting rubber materials to be stretched on an inside of an automobile door so as to prevent rain or wind from entering the automobile interior from outside are readily punched.

The shape of the hole punched with the puncher P as described above is circular, but not limitative thereto, and may be elliptical, oval, or another shape.

The puncher P according to the above embodiment has an extremely downsized structure with an entire length of 72 mm and an attaching portion 12 shaped in a triangle with 32 mm length and 30 mm wide.

The puncher P may be mounted on a slide cam die shown in FIG. 8 of Japanese Patent Application Laid-Open No. 2006-61938 to punch a hole in a workpiece. 

1. A puncher comprising: a cylindrical cover with a one-end opening hole; a piercing punch, a tip end surface of which is protruded from the one-end opening hole, and which is loosely but not removably inserted with respect to the cover; a cylindrical stripper provided between the cover and the piercing punch in a retaining state; a biasing member by which the stripper is protruded more than the piercing punch from the one-end opening hole; and wherein, when the stripper is pressed in against biasing force of the biasing member, the tip end surface of the piercing punch becomes protruded out from a through-hole formed at a protruding end of the stripper, the cover is made of metal, and a diameter of a second cover portion of the cover at and near the one-end opening hole side is smaller than that of a first cover portion other than the second portion.
 2. The puncher according to claim 1, wherein the first cover portion receives the biasing member.
 3. The puncher according to claim 2, wherein the second cover portion reduces in diameter toward the opening hole to form a tapered portion.
 4. The puncher according to claim 3, wherein an inclining line of the tapered portion is concave inwardly.
 5. The puncher according to claim 1, wherein the biasing member is a compression coil spring.
 6. The puncher according to claim 1, wherein piercing process is conducted by the piercing punch while a workpiece is kept pressed by the stripper. 